# Problem P. 4099. (October 2008)

**P. 4099.** A sample of water of mass *m*_{1} and of temperature *t*_{1} is in a thermos flask, and warmer water of mass *m*_{2} and of temperature *t*_{2} is poured to it. After the themal equilibrium is reached the temperature is measured. Next time, because we are curious, we swop the two samples of water, so the colder water of mass *m*_{1} and of temperature *t*_{1} is poured into the thermos in which there is the other sample of water of mass *m*_{2} and of temperature *t*_{2}. Surprisingly it is found that the equilibrium temperature in the second case is different from the one measured in the first time.

*a*) How can you explain this difference?

*b*) The difference between the two equilibrium temperatures is 1.9 ^{o}C. What can you deduce from this?

*Data:* *m*_{1}=300 g, *t*_{1}=20 ^{o}C, *m*_{2}=600 g, *t*_{2}=80 ^{o}C.

(4 pont)

**Deadline expired on November 11, 2008.**

### Statistics:

118 students sent a solution. 4 points: 80 students. 3 points: 15 students. 2 points: 15 students. 1 point: 4 students. 0 point: 2 students. Unfair, not evaluated: 2 solutions.

Problems in Physics of KöMaL, October 2008